A simple and effective separation of UO2 and Ln2O3 assisted by NH4Cl in LiCl–KCl eutectic

Abstract For UO2-based spent fuel, it is usually electrochemically reduced and then refined in molten salt with respect to the so-called pyrochemical reprocessing approach. In this work, we report a new method with the assistance of NH4Cl to directly achieve convenient separation of UO2 over La2O3 in Ar atmosphere which does not require an electrochemical process. According to the results from both powder and pellet samples, the separation is achieved by dissolving La2O3 into the LiCl–KCl molten salt with NH4Cl, whilst UO2 cannot be dissolved and remains in solid form. It was found that the dissolution kinetics of La2O3 in the powder sample was fast and its removal efficiency in the mixture of La2O3 and UO2 was high, but a specific amount of UO2 was also dissolved, which lead to a low recovery efficiency of UO2. In contrast, when the pellet samples after sintering at 1473 K were used, the recovery efficiency of UO2 can be increased. Nevertheless, the dissolution kinetics of La2O3 was correspondingly reduced, and more NH4Cl was required to complete the dissolution reaction. By improving and optimizing the experimental conditions, the UO2 recovery efficiency of 92.0% can be achieved, while the removal efficiency of La2O3 was 94.4%. More importantly, this novel separation method may be also useful for the separation of UO2 over mixed lanthanide oxides.